If your dentist is subjecting you to excruciating pain, I suggest you find a different dentist. Most dental procedures are completely pain-free these days. Some have residual soreness once the shot wears off; that's what they make Vicoden for.

With the sort of logic that is popular these days we would have rejected fire as unsafe (radiation from a fire is higher frequency than this THz - i.e. very far infrared) and still be eating our food raw in unheated caves.

There is no such thing as "completely safe". The idea is preposterous. It is even more preposterous that we can prove something to be completely safe. Every heartbeat or breath you take is at great risk.

It's all about rational risk assessment and testing. Given the fundamentals here there is no reason to be concerned about the safety of terahertz radiation. It is certainly far safer than the alternatives which have large known risks.

The problem isn't that it involves risk, it is that things that are "completely safe" eventually get abused to the point that they are no longer safe. X-Rays can cause cancer, but we know that x-rays cause cancer and therefore doctors/dentists are more reluctant to use them. Back when X-rays were considered 100% safe, we used them to see how well shoes fit! And other novelties.

Is terahertz radiation safer than x-rays? Quite possibly. If we use terahertz radiation to excess will it be safer than x-rays? Quite possibly not.

I agree, but we shouldn't use the name "completely safe" until it's tested and proven to be safe.

Why don't we just all agree to call all these technologies "Mostly Harmless" until proven otherwise.

Then there will be no confusion.

And if there is confusion, the idiots who are confused need to learn to read, then read a good book. A good book written by Douglas Adams. Then they will understand. They will understand in exactly the same way that bricks don't.

No doctor or dentist I've ever been to was ever 'reluctant' to call for an x-ray. As long as you're insured, it's free money for them to call for an x-ray, whether you need it or not. Last time I went in for neck pain, the doctor actually told me that whatever was causing my pain would most likely only show up on an MRI (as it was most likely due to tissue, not bone, issues), but he wanted to take an x-ray "just to see", and that he'd call for an MRI only if I still had pain a week or two later.

As long as every doctor/dentist has an x-ray machine in-house that they can charge your insurance company for, whether it's really needed or not, they'll use it. If we can replace x-ray with some other most likely less-harmful tech, I'm in.

Drinking tap water is safe. So you wouldn't mind if I submerged you in a tub of it for an hour?Playing tennis is safe. So you wouldn't mind if I made you play in a hurricane?Reading slashdot is safe. So you wouldn't mind if I made you sit there reading it for a week while force feeding you cheetos?

Because even that is a distortion. We should call such technologies "new" and anybody who calls them "safe" should be required to either produce evidence that says it is so or a bond that will be paid to whoever eventually suffers harm due to them.

When the dentist takes x-rays, they first cover me with a lead blanket from neck to knee and then they leave the room while the pictures are being taken. That's because we know that x-rays are dangerous, and we understand how they're dangerous and what steps should be taken to minimize the risk while still taking advantage of the technology.

If it's "perfectly safe", no such precautions will be taken. Decades from now, we'll know whether they should have been.

There is very good evidence that terahertz waves are anything but safe!

Whereas X-rays pass through most body parts, leading to a very low rate of absorption that is also spread throughout most of the body, terahertz waves are the opposite: a minority of the radiation is reflected back to the scanner, but the majority is completely absorbed by the tissue at the depth of penetration. And because that depth is pretty specific, what you have is a very thin layer of tissue that is completely absorbing a great deal of energy from the radiation.

If you really think about that, you will change your mind about any "completely safe" claims. We need tests and more tests and double-blind tests, before it can be declared "safe", and even then we would need to wait for a long time to rule out any possible long-term effects.